1. Field of Invention
The present invention relates generally to the construction and use of vascular and other catheters. More particularly, the invention relates to intravascular catheters with a housing and a window on a lateral side of the housing for surgical intervention within a biological conduit.
2. Previous Art
Arteriosclerosis, also known as atherosclerosis, is a common human ailment arising from the deposition of fat-like substances, referred to as atheroma or plaque, on the walls of blood vessels. Such deposits occur both in peripheral blood vessels that feed the limbs of the body and in coronary blood vessels that feed the heart. When deposits accumulate in localized regions of a blood vessel, the regions become stenosed, blood flow is restricted, and the person's health is at serious risk.
Numerous approaches for reducing and removing such stenotic deposits have been proposed, including balloon angioplasty, where a balloon-tipped catheter is used to dilate the stenosed region, atherectomy, where a blade or other cutting element is used to sever and remove stenotic material, and laser angioplasty, where laser energy is used to ablate at least a portion of the stenotic material.
Typically, while using an atherectomy catheter a cutting blade is advanced past an opening in a housing at the distal end of a vascular catheter. By positioning the housing so that at least a portion of the stenotic material passes through the opening, the stenotic material can be severed and translated forward by advancing the cutting blade. Typically, such cutting blades are circular, and are rotated and advanced simultaneously to affect the desired cutting.
Atherectomy catheters are described in U.S. Pat. Nos. 4,669,469; 4,781,186; 4,926,858; 4,979,951; 5,047,040; 5,084,010; and reissued Pat. No. Re. 33,569. Of these, the U.S. Pat. Nos. 4,926,858 and 5,047,040 patents describe atherectomy catheters having rotating cutters which are extended distally through an opening in the distal end of a housing to penetrate and/or remove stenotic material in the vessel. The U.S. Pat. No. 4,979,951 and Re. 33,569 patents describe catheters having distal housings where a rotatable cutting blade receives a coaxial movable guidewire. The U.S. Pat. No. 4,781,186 patent describes atherectomy catheters having flexible distal housing. U.S. Pat. No. 5,250,059, Issue Date, Oct. 5, 1993, assigned to the assignee of the present application, describes an atherectomy catheter having a flexible nose cone attached to the distal end of a cutter housing.
The atherectomy catheters disclosed above have enjoyed widespread success in both peripheral and coronary applications. However, in known atherectomy catheters, the cutting blade cannot be withdrawn proximally from the housing due to various factors including the connection structures used for connecting the housing to the distal end of the catheter body, as well as clearance limitations in the interior of the catheter body. Situations arise in which it would be desirable to withdraw the cutting blade from the housing while leaving the catheter body and distal housing positioned in the vessel.
For example, if the vessel lumen becomes blocked by a combination of stenosis and the catheter housing, it is desirable to withdraw the cutter from the housing in order to provide blood bypass through the device for perfusion of tissue downstream of the catheter. In another example, the work element may need to be replaced before the task is finished. Moreover, there are situations in which it would be desirable to completely withdraw the cutting blade from the catheter, for purposes such as exchanging the cutter for a different type of work element to perform other interventional procedures such as imaging, drug delivery, dilatation, laser ablation and the like. If it is desired to perform more than one procedure at a treatment site, atherectomy catheters presently in use require that the catheter, including the catheter body, be entirely withdrawn from the vessel and replaced and repositioned with an entirely new catheter having the desired type of work element.
For these and other reasons, catheter designs are desired of the type in which a housing is attached to the distal end of a catheter body, the housing having a window for directional intervention in a biological conduit. In particular, it is desirable to allow the housing to be positioned in a biological conduit to have its related work element interchanged without removing the housing. It would be desirable for such an improved catheter to include a flow bypass for flowing blood through the housing with the work element in place, for perfusion of tissue downstream of the work element. Such an improved catheter should permit the work element to be withdrawn from the housing into a receiving space in the catheter body. Most desirably, such an improved catheter permits the work element to be completely withdrawn from the proximal end of the catheter body, to allow interchange of various work elements, such as rotating and reciprocating cutters, abrasive grinding elements, dilatation devices, ultrasonic and angioscopic imaging devices and laser ablation devices, ultrasonic or mechanical vibrating elements that alter vessel compliance, among others.